From: Daniel Vetter Date: Mon, 4 Jan 2016 06:53:36 +0000 (+0100) Subject: drm/docs: more leftovers from the big vtable documentation pile X-Git-Url: https://git.stricted.de/?a=commitdiff_plain;h=df7d678bea8ba8904bdb293c8e96aa9488f7dbee;p=GitHub%2FLineageOS%2Fandroid_kernel_motorola_exynos9610.git drm/docs: more leftovers from the big vtable documentation pile Another pile of vfuncs from the old gpu.tmpl xml documentation that I've forgotten to delete. I spotted a few more things to clarify/extend in the new kerneldoc while going through this once more. v2: Spelling fixes (Thierry). v3: More spelling fixes and use Thierry's proposal to clarify why drivers need to validate modes both in ->mode_fixup and ->mode_valid. Cc: Laurent Pinchart Cc: Thierry Reding Acked-by: Thierry Reding Signed-off-by: Daniel Vetter --- diff --git a/Documentation/DocBook/gpu.tmpl b/Documentation/DocBook/gpu.tmpl index 225a246c5f53..faa5e0d4208d 100644 --- a/Documentation/DocBook/gpu.tmpl +++ b/Documentation/DocBook/gpu.tmpl @@ -1578,194 +1578,6 @@ void intel_crt_init(struct drm_device *dev) To use it, a driver must provide bottom functions for all of the three KMS entities. - - Legacy CRTC Helper Operations - - - bool (*mode_fixup)(struct drm_crtc *crtc, - const struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Let CRTCs adjust the requested mode or reject it completely. This - operation returns true if the mode is accepted (possibly after being - adjusted) or false if it is rejected. - - - The mode_fixup operation should reject the - mode if it can't reasonably use it. The definition of "reasonable" - is currently fuzzy in this context. One possible behaviour would be - to set the adjusted mode to the panel timings when a fixed-mode - panel is used with hardware capable of scaling. Another behaviour - would be to accept any input mode and adjust it to the closest mode - supported by the hardware (FIXME: This needs to be clarified). - - - - int (*mode_set_base)(struct drm_crtc *crtc, int x, int y, - struct drm_framebuffer *old_fb) - - Move the CRTC on the current frame buffer (stored in - crtc->fb) to position (x,y). Any of the frame - buffer, x position or y position may have been modified. - - - This helper operation is optional. If not provided, the - drm_crtc_helper_set_config function will fall - back to the mode_set helper operation. - - - FIXME: Why are x and y passed as arguments, as they can be accessed - through crtc->x and - crtc->y? - - - - void (*prepare)(struct drm_crtc *crtc); - - Prepare the CRTC for mode setting. This operation is called after - validating the requested mode. Drivers use it to perform - device-specific operations required before setting the new mode. - - - - int (*mode_set)(struct drm_crtc *crtc, struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode, int x, int y, - struct drm_framebuffer *old_fb); - - Set a new mode, position and frame buffer. Depending on the device - requirements, the mode can be stored internally by the driver and - applied in the commit operation, or - programmed to the hardware immediately. - - - The mode_set operation returns 0 on success - or a negative error code if an error occurs. - - - - void (*commit)(struct drm_crtc *crtc); - - Commit a mode. This operation is called after setting the new mode. - Upon return the device must use the new mode and be fully - operational. - - - - - - Encoder Helper Operations - - - bool (*mode_fixup)(struct drm_encoder *encoder, - const struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Let encoders adjust the requested mode or reject it completely. This - operation returns true if the mode is accepted (possibly after being - adjusted) or false if it is rejected. See the - mode_fixup CRTC helper - operation for an explanation of the allowed adjustments. - - - - void (*prepare)(struct drm_encoder *encoder); - - Prepare the encoder for mode setting. This operation is called after - validating the requested mode. Drivers use it to perform - device-specific operations required before setting the new mode. - - - - void (*mode_set)(struct drm_encoder *encoder, - struct drm_display_mode *mode, - struct drm_display_mode *adjusted_mode); - - Set a new mode. Depending on the device requirements, the mode can - be stored internally by the driver and applied in the - commit operation, or programmed to the - hardware immediately. - - - - void (*commit)(struct drm_encoder *encoder); - - Commit a mode. This operation is called after setting the new mode. - Upon return the device must use the new mode and be fully - operational. - - - - - - Connector Helper Operations - - - struct drm_encoder *(*best_encoder)(struct drm_connector *connector); - - Return a pointer to the best encoder for the connecter. Device that - map connectors to encoders 1:1 simply return the pointer to the - associated encoder. This operation is mandatory. - - - - int (*get_modes)(struct drm_connector *connector); - - Fill the connector's probed_modes list - by parsing EDID data with drm_add_edid_modes, - adding standard VESA DMT modes with drm_add_modes_noedid, - or calling drm_mode_probed_add directly for every - supported mode and return the number of modes it has detected. This - operation is mandatory. - - - Note that the caller function will automatically add standard VESA - DMT modes up to 1024x768 if the get_modes - helper operation returns no mode and if the connector status is - connector_status_connected. There is no need to call - drm_add_edid_modes manually in that case. - - - The vrefresh value is computed by - drm_helper_probe_single_connector_modes. - - - When parsing EDID data, drm_add_edid_modes fills the - connector display_info - width_mm and - height_mm fields. When creating modes - manually the get_modes helper operation must - set the display_info - width_mm and - height_mm fields if they haven't been set - already (for instance at initialization time when a fixed-size panel is - attached to the connector). The mode width_mm - and height_mm fields are only used internally - during EDID parsing and should not be set when creating modes manually. - - - - int (*mode_valid)(struct drm_connector *connector, - struct drm_display_mode *mode); - - Verify whether a mode is valid for the connector. Return MODE_OK for - supported modes and one of the enum drm_mode_status values (MODE_*) - for unsupported modes. This operation is optional. - - - As the mode rejection reason is currently not used beside for - immediately removing the unsupported mode, an implementation can - return MODE_BAD regardless of the exact reason why the mode is not - valid. - - - Note that the mode_valid helper operation is - only called for modes detected by the device, and - not for modes set by the user through the CRTC - set_config operation. - - - - Atomic Modeset Helper Functions Reference diff --git a/include/drm/drm_modeset_helper_vtables.h b/include/drm/drm_modeset_helper_vtables.h index 29e0dc50031d..a126a0d7aed4 100644 --- a/include/drm/drm_modeset_helper_vtables.h +++ b/include/drm/drm_modeset_helper_vtables.h @@ -131,6 +131,20 @@ struct drm_crtc_helper_funcs { * Atomic drivers which need to inspect and adjust more state should * instead use the @atomic_check callback. * + * Also beware that neither core nor helpers filter modes before + * passing them to the driver: While the list of modes that is + * advertised to userspace is filtered using the connector's + * ->mode_valid() callback, neither the core nor the helpers do any + * filtering on modes passed in from userspace when setting a mode. It + * is therefore possible for userspace to pass in a mode that was + * previously filtered out using ->mode_valid() or add a custom mode + * that wasn't probed from EDID or similar to begin with. Even though + * this is an advanced feature and rarely used nowadays, some users rely + * on being able to specify modes manually so drivers must be prepared + * to deal with it. Specifically this means that all drivers need not + * only validate modes in ->mode_valid() but also in ->mode_fixup() to + * make sure invalid modes passed in from userspace are rejected. + * * RETURNS: * * True if an acceptable configuration is possible, false if the modeset @@ -188,7 +202,9 @@ struct drm_crtc_helper_funcs { * This callback is used by the legacy CRTC helpers to set a new * framebuffer and scanout position. It is optional and used as an * optimized fast-path instead of a full mode set operation with all the - * resulting flickering. Since it can't update other planes it's + * resulting flickering. If it is not present + * drm_crtc_helper_set_config() will fall back to a full modeset, using + * the ->mode_set() callback. Since it can't update other planes it's * incompatible with atomic modeset support. * * This callback is only used by the CRTC helpers and deprecated. @@ -439,6 +455,20 @@ struct drm_encoder_helper_funcs { * Atomic drivers which need to inspect and adjust more state should * instead use the @atomic_check callback. * + * Also beware that neither core nor helpers filter modes before + * passing them to the driver: While the list of modes that is + * advertised to userspace is filtered using the connector's + * ->mode_valid() callback, neither the core nor the helpers do any + * filtering on modes passed in from userspace when setting a mode. It + * is therefore possible for userspace to pass in a mode that was + * previously filtered out using ->mode_valid() or add a custom mode + * that wasn't probed from EDID or similar to begin with. Even though + * this is an advanced feature and rarely used nowadays, some users rely + * on being able to specify modes manually so drivers must be prepared + * to deal with it. Specifically this means that all drivers need not + * only validate modes in ->mode_valid() but also in ->mode_fixup() to + * make sure invalid modes passed in from userspace are rejected. + * * RETURNS: * * True if an acceptable configuration is possible, false if the modeset @@ -640,8 +670,16 @@ struct drm_connector_helper_funcs { * In this function drivers then parse the modes in the EDID and add * them by calling drm_add_edid_modes(). But connectors that driver a * fixed panel can also manually add specific modes using - * drm_mode_probed_add(). Finally drivers that support audio probably - * want to update the ELD data, too, using drm_edid_to_eld(). + * drm_mode_probed_add(). Drivers which manually add modes should also + * make sure that the @display_info, @width_mm and @height_mm fields of the + * struct #drm_connector are filled in. + * + * Virtual drivers that just want some standard VESA mode with a given + * resolution can call drm_add_modes_noedid(), and mark the preferred + * one using drm_set_preferred_mode(). + * + * Finally drivers that support audio probably want to update the ELD + * data, too, using drm_edid_to_eld(). * * This function is only called after the ->detect() hook has indicated * that a sink is connected and when the EDID isn't overridden through